Off to the Alps soon and I've got a bit of a dodgy wrist due to a break about 4yrs ago and a recent knock seems to have aggravated it a bit.

Has anyone used one of the 661 wrist supports for riding? What are they like in terms of obtrusiveness, etc?

Hi, not too sure about the seperate supports but a friend used to have gloves with a wrist support built in which were very good.

I highly recommend this one:
661 Wrist Wrap Pro

I have used it for 20 months with a fractured scaphoid (that I didn't know I had). It has prevented more damage from being done in several big crashes and am now getting it pinned so should make a full recovery with no necrosis of the bone. If I hadn't been wearing it, I would have definitely screwed the wrist up more (possibly for good!).
I tried another 661 wrist support but it didn't feel as strong and supportive as this one. It does look a bit stupid but it does a good job. Having now sprained my other wrist, I am getting a second one to prevent any further wrist damage in the future!

I had a problem with wrist a couple of years ago. I used a pair of Ergon grips for while. Found it a lot less strain on my wrist, look a bit funny, but would recommend them for weaker wrists.

The Pro looked a bit bulky, does it let you still grip the bars okay and stuff?

Another vote for the 661 Wrist Wrap Pro here.
Its not at all bulky as none of the wrist support actually goes under the palm of the hand. You can also wear gloves with it too!

Also use a 661 wrist support, broke my wrist badly a year ago and had a metal plate put in, the wrist wrap does feel quite weird for a bit, but it isn't really obtrusive and you don't notice it after a few rides, worth using for piece of mind IMO…

Yep 3rd the wrist wrap Pro,

Broke my left radius twice in the same place and the support works a treat. Not too bulky and I feel more confidant when using it.

I've got one of the 661 race wrist braces, offers plenty of support, but won't go under gloves, however doesn't feel uncomfortable to wear.

2nd what everyone else has said about 661 Wrist Wraps, they are pretty good. But if it's an old injury which has left your wrist weaker for whatever reason then you might be better off trying to build it up (Powerballs are pretty good) once the current problems have subsided.

I have a 661 too.

It doesn't do anything for me on the bike but I suspect it would help protect me if I came off.

But to be honest I rarely use it.